Since licensure of the Haemophilus influenzae type b (Hib) conjugate vaccines for young infants, there is strong evidence that Hib invasive disease is disappearing. Streptococcus pneumoniae (pneumococcus) has accordingly assumed a bigger role in the incidence of invasive disease in infants and young children, and has also been implicated in otitis media. Consequently, pneumococcus warrants a focused vaccine development effort. This contract will support a reference and resource laboratory for studies of pneumococcal polysaccharide conjugate vaccines. These vaccines are considerably more complex that the Hib conjugate vaccines: there are numerous disease-causing serotypes and a vaccine will need to be multivalent; the chemistry of conjugation to some of the serotypes is technically challenging; and multiple carriers may be needed. Assays will be complex and without a standardized assay, efforts to diagnose disease, and to evaluate vaccine immunogenicity and efficacy will be compromised. The pneumococcal reference laboratory will: 1) contribute to the development and optimization of a standardized pneumococcal antibody assay, 2) serve as a reference center through which assays will be standardized for the vaccine community, 3) prepare antigens and reagents, and 4) perform serological assays. This contract will also continue to make available antigens and critical reagents for Hib assays.